Hi Luis, On Fri, Jun 5, 2020 at 12:50 AM Luis Machado <luis.machado@xxxxxxxxxx> wrote: > > 1 - x86-64 seems to get an extra SIGSTOP when we single-step over the > vfork syscall, though this doesn't seem to do any harm. Is it possible that on arm64 you attached to the original tracee using PTRACE_SEIZE, but used some other method on x86-64? That would explain this difference. > 2 - This is the one that throws GDB off. In the last single-step > request, arm64 gets a SIGCHLD instead of the SIGTRAP x86-64 gets. I believe this is ok. The timing of SIGCHLD is not guaranteed, so it's allowed to pre-empt the single step. I have seen some differences in signal delivery order on arm64, but I believe it just comes down to scheduling and performance differences between the systems, since these interactions are a bit racy. Keno
